The structure of a sample surface can be observed by irradiating the sample with an electron while scanning and detecting secondary charged particles released from the sample. This is called a scanning electron microscope (hereinafter abbreviated as SEM). The structure of the sample surface can be observed even by irradiating the sample with an ion beam while scanning and detecting secondary charged particles released from the sample. This is called a scanning ion microscope (hereinafter abbreviated as SIM). In particular, if the sample is irradiated with the ion species of light mass such as hydrogen and helium, the sputtering action becomes relatively small and it becomes suitable for observing the sample.
Furthermore, the ion beam has a characteristic of being sensitive to information on the sample surface compared to the electron beam. This is because an excitation region of the secondary charged particle is localized by the sample surface compared to the irradiation of the electron beam. Aberration is generated by a diffraction effect in the electron beam as the property for the wave of the electron cannot be ignored. The diffraction effect can be ignored in the ion beam as the ion beam is heavy compared to the electron.
The information reflecting the structure of the inside of the sample can be obtained by irradiating the sample with the ion beam, and detecting the ion transmitted through the sample. This is called a transmission ion microscope. In particular, if the sample is irradiated with the ion species of light mass such as hydrogen and helium, it becomes suitable for observation as the proportion of the ion that transmits through the sample becomes large.
On the contrary, irradiating the sample with the ion species of heavy mass such as argon, xenon, and gallium is suitable for processing the sample by the sputtering action. In particular, a focused ion beam device (hereinafter referred to as FIB) using a liquid metal ion source (hereinafter referred to as LMIS) is known as an ion beam processing device. Furthermore, a combined FIB-SEM device of the scanning electron microscope (SEM) and the focused ion beam (FIB) is also used in recent years. In the FIB-SEM device, the FIB is irradiated to form a square hole at the desired area so that the cross-section can be SEM observed. The sample can be processed even by generating a gas ion such as argon and xenon with a plasma ion source and a gas field ion source, and irradiating the sample with the same.
In the ion microscope, the gas field ion source is suitable for the ion source. The gas field ion source can generate an ion beam having a narrow energy width. Furthermore, the ion generation source can generate a microscopic ion beam since the size is small.
In the ion microscope, an ion beam of large current density needs to be obtained on the sample to observe the sample at a high signal/noise ratio. To this end, an ion emission angle current density of the gas field ion source needs to be large. The molecular density of the ion material gas (ionized gas) near the emitter tip merely needs to be made large to increase the ion emission angle current density. The gas molecular density per unit pressure is inversely proportional to the temperature of the gas. Thus, the emitter tip is cooled to an extremely low temperature, and the temperature of the gas around the emitter tip is to be lowered. The molecular density of the ionized gas near the emitter tip thus can be made large. The pressure of the ionized gas around the emitter tip can be set to about 10−2 to 10 Pa.
However, if the pressure of the ion material gas is greater than or equal to ˜1 Pa, the ion beam collides with a neutral gas and neutralizes, whereby the ion current lowers. When the number of gas molecules in the gas field ion source increases, the frequency of the gas molecules, the temperature of which is increased by colliding with the vacuum chamber wall of high temperature, which collide with the emitter tip becomes high. The temperature of the emitter tip thus rises and the ion current lowers. To this end, a gas ionization chamber that mechanically surrounds the periphery of the emitter tip is arranged in the gas field ion source. The gas ionization chamber is formed using an ion extraction electrode arranged facing the emitter tip.
Patent document 1 discloses enhancing the ion source characteristics by forming a microscopic projection at the distal end of the emitter tip. Non-patent document 1 discloses forming the microscopic projection at the distal end of the emitter tip using a second metal different from the material of the emitter tip. Non-patent document 2 discloses a scanning ion microscope mounted with the gas field ion source for ion releasing helium.
Patent document 2 discloses a gas field ion source in which a bellows is arranged in the ionization chamber. However, in such gas field ion source, the problem in which the ionization chamber is contacted to room temperature through a sample chamber wall, and the gas supplied to the ionization chamber collides with the sample chamber wall of high temperature is not mentioned. The description related to the inclination of the emitter tip is also not made.
Patent document 3 discloses a gas field ion source arranged with a direction adjustment mechanism for varying the axis direction of the ion source. However, in such gas field ion source, the problem in which the ionization chamber is contacted to room temperature through a sample chamber wall, and the gas supplied to the ionization chamber collides with the sample chamber wall of high temperature is not mentioned. Furthermore, the extraction electrode inclines with the change in axis direction of the ion source.
Patent document 4 discloses a gas field ion source arranged with a switching switch for connecting an extraction electrode high voltage lead-in wire to an emitter tip high voltage lead-in wire. In such gas field ion source, the discharge between the emitter tip and the extraction electrode can be prevented after the so-called conditioning process or an enforced discharging process between the ion source outer wall and the emitter tip.
Patent document 5 discloses a charged beam device in which a vibration proofing tool is arranged between a base plate for mounting the main body of the charged particle device and a device mount. However, the description related to a cooling mechanism of the charged particle source is not made at all in patent document 5.
Patent document 6 proposes a device for observing and analyzing defects, foreign substances, and the like by forming a square hole in the vicinity of an abnormal area of a sample with the FIB and observing the cross-section of the square hole with the SEM device. Patent document 7 proposes a technique of extracting a microscopic sample for transmission electron microscope observation from a bulk sample using the FIB and the probe.    Patent document 1: Japanese Laid-Open Patent Publication No. 58-85242    Patent document 2: Japanese Patent Publication NO. 3-74454    Patent document 3: Japanese Laid-Open Patent Publication No. 62-114226    Patent document 4: Japanese Laid-Open Patent Publication No. 1-221847    Patent document 5: Japanese Laid-Open Patent Publication No. 8-203461    Patent document 6: Japanese Laid-Open Patent Publication No. 2002-150990    Patent document 7: International Patent Publication WO99/05506    Non-patent document 1: H. -S. Kuo, I. -S. Hwang, T. -Y. Fu, J. -Y. Wu, C. -C. Chang, and T. T. Tsong, Nano Letters 4 (2004) 2379.    Non-patent document 2: J. Morgan, J. Notte, R. Hill, and B. Ward, Microscopy Today, Jul. 14 (2006) 24